Encapsulated solid hydrophilic particles

ABSTRACT

A process of forming microcapsules is described. The microcapsule population is formed by providing an anionic or cationic, solid hydrophilic core material; providing an oil continuous phase, the oil continuous phase comprising one or more esters with chain length up to about 18 carbons. Emulsification is achieved by subjecting the mixture to high shear agitation and heating the mixture for a time sufficient to enable acid or amine acrylate or methacrylate and multifunctional acrylate or methacrylate to form a prepolymer which migrates to the anionic or cationic solid hydrophilic material, thereby forming prepolymers adhered to the hydrophilic core materials. Temperature is held or heating continued for a time sufficient to enable the prepolymer to flow onto and coalesce into a continuous film surface coating on the hydrophilic core material. Heating is carried out or light exposure or both for a time and temperature sufficient to cross link the prepolymers.

This application is a divisional application and claims benefit under 35U.S.C. §120 and §121 of U.S. Ser. No. 12/754,900 filed Apr. 6, 2010, nowpending which claims benefit per 35 USC §119(e) to application Ser. No.61/167,336 filed Apr. 7, 2009 as a provisional application per 35 USC§111(b)

FIELD OF THE INVENTION

This invention relates to capsule manufacturing processes andmicrocapsules produced by such processes.

DESCRIPTION OF THE RELATED ART

Various processes for microencapsulation, and exemplary methods andmaterials are set forth in Schwantes (U.S. Pat. No. 6,592,990), Nagaiet. al. (U.S. Pat. No. 4,708,924), Baker et. al. (U.S. Pat. No.4,166,152), Wojciak (U.S. Pat. No. 4,093,556), Matsukawa et. al. (U.S.Pat. No. 3,965,033), Matsukawa (U.S. Pat. No. 3,660,304), Ozono (U.S.Pat. No. 4,588,639), Irgarashi et. al. (U.S. Pat. No. 4,610,927), Brownet. al. (U.S. Pat. No. 4,552,811), Scher (U.S. Pat. No. 4,285,720),Shioi et. al. (U.S. Pat. No. 4,601,863), Kiritani et. al. (U.S. Pat. No.3,886,085), Jahns et. al. (U.S. Pat. Nos. 5,596,051 and 5,292,835),Matson (U.S. Pat. No. 3,516,941), Chao (U.S. Pat. No. 6,375,872), Foriset. al. (U.S. Pat. Nos. 4,001,140; 4,087,376; 4,089,802 and 4,100,103),Greene et. al. (U.S. Pat. Nos. 2,800,458; 2,800,457 and 2,730,456),Clark (U.S. Pat. No. 6,531,156), Saeki et. al. (U.S. Pat. Nos. 4,251,386and 4,356,109), Hoshi et. al. (U.S. Pat. No. 4,221,710), Hayford (U.S.Pat. No. 4,444,699), Hasler et. al. (U.S. Pat. No. 5,105,823), Stevens(U.S. Pat. No. 4,197,346), Riecke (U.S. Pat. No. 4,622,267), Greiner et.al. (U.S. Pat. No. 4,547,429), and Tice et. al. (U.S. Pat. No.5,407,609), among others and as taught by Herbig in the chapter entitled“Microencapsulation” in Kirk-Othmer Encyclopedia of Chemical Technology,V.16, pages 438-463.

More particularly, U.S. Pat. Nos. 2,730,456; 2,800,457; and 2,800,458describe methods for capsule formation. Other useful methods formicrocapsule manufacture are: U.S. Pat. Nos. 4,001,140; 4,081,376 and4,089,802 describing a reaction between urea and formaldehyde; U.S. Pat.No. 4,100,103 describing reaction between melamine and formaldehyde;British Pat. No. 2,062,570 describing a process for producingmicrocapsules having walls produced by polymerization of melamine andformaldehyde in the presence of a styrenesulfonic acid. Formingmicrocapsules from urea-formaldehyde resin and/or melamine formaldehyderesin is disclosed in U.S. Pat. Nos. 4,001,140; 4,081,376, 4,089,802;4,100,103; 4,105,823; and 4,444,699. Alkyl acrylate-acrylic acidcopolymer capsules are taught in U.S. Pat. No. 4,552,811. Each patentdescribed throughout this application is incorporated herein byreference to the extent each provides guidance regardingmicroencapsulation processes and materials.

Interfacial polymerization is a process wherein a microcapsule wall of apolyamide, an epoxy resin, a polyurethane, a polyurea or the like isformed at an interface between two phases. U.S. Pat. No. 4,622,267discloses an interfacial polymerization technique for preparation ofmicrocapsules. The core material is initially dissolved in a solvent andan aliphatic diisocyanate soluble in the solvent mixture is added.Subsequently, a nonsolvent for the aliphatic diisocyanate is added untilthe turbidity point is just barely reached. This organic phase is thenemulsified in an aqueous solution, and a reactive amine is added to theaqueous phase. The amine diffuses to the interface, where it reacts withthe diisocyanate to form polymeric polyurethane shells. A similartechnique, used to encapsulate salts which are sparingly soluble inwater in polyurethane shells, is disclosed in U.S. Pat. No. 4,547,429.U.S. Pat. No. 3,516,941 teaches polymerization reactions in which thematerial to be encapsulated, or core material, is dissolved in anorganic, hydrophobic oil phase which is dispersed in an aqueous phase.The aqueous phase has dissolved materials forming aminoplast resin whichupon polymerization form the wall of the microcapsule. A dispersion offine oil droplets is prepared using high shear agitation. Addition of anacid catalyst initiates the polycondensation forming the aminoplastresin within the aqueous phase, resulting in the formation of anaminoplast polymer which is insoluble in both phases. As thepolymerization advances, the aminoplast polymer separates from theaqueous phase and deposits on the surface of the dispersed droplets ofthe oil phase to form a capsule wall at the interface of the two phases,thus encapsulating the core material. Urea-formaldehyde (UF),urea-resorcinol-formaldehyde (URF), urea-melamine-formaldehyde (UMF),and melamine-formaldehyde (MF), capsule formations proceed in suchmanner.

In interfacial polymerization, the materials to form the capsule wallare in separate phases, one in an aqueous phase and the other in a fillphase. Polymerization occurs at the phase boundary. Thus, a polymericcapsule shell wall forms at the interface of the two phases therebyencapsulating the core material. Wall formation of polyester, polyamide,and polyurea capsules typically proceeds via interfacial polymerization.

Jans et al., U.S. Pat. No. 5,292,835 teaches polymerizing esters ofacrylic acid or methacrylic acid with polyfunctional monomers.Specifically illustrated are reactions of polyvinylpyrrolidone withacrylates such as butanediol diacrylate or methylmethacrylate togetherwith a free radical initiator to form capsules surrounding an oil core.

Common microencapsulation processes can be viewed as a series of steps.First, the core material which is to be encapsulated typically on oil isemulsified or dispersed in a suitable dispersion medium. This medium istypically aqueous but involves the formation of a polymer rich phase.Most frequently, this medium is a solution of the intended capsule wallmaterial. The solvent characteristics of the medium are changed such asto cause phase separation of the wall material. The wall material isthereby contained in a liquid phase which is also dispersed in the samemedium as the intended capsule core material. The liquid wall materialphase deposits itself as a continuous coating about the disperseddroplets of the emulsified oil.

In the present invention the core is typically solid, and moreparticularly a solid, especially at room temperature, and constituting asolid hydrophilic material.

Many solid hydrophilic materials are water sensitive. Sunol et al. U.S.Patent Application 20070289720 at the University of South Floridadescribes a self heating chemical system based on solid water sensitiveparticles involving calcium oxide, zeolite and citric acid physicallyseparated from water which then undergo an exothermine reaction when apouch containing water is ruptured.

Wheeler et al., U.S. Patent Application 20080304447 describe timedelayed activation of zeolite heating wherein zeolite particles arecoated with molten polyethylene, melted waxes or molten sucrose octylstearate. Such coated particles when contacted with water yield a timedelayed heat release cosmetic or facial cleanser.

Zeolites are useful solid hydrophilic materials. Zeolites have theproperty to attract (adsorb) water vapor and to incorporate it in itsinternal crystal lattice while releasing heat at the same time. If thisprocess proceeds in an evacuated (airless) environment the attraction ofwater by the zeolite is so forceful that the internal pressure dropsdramatically. The remaining water in an attached vessel evaporates,cools down and freezes immediately due to the heat of evaporation. Theresulting ice can be used for cooling and air conditioning while thesimultaneously produced heat of adsorption within the zeolite tank canbe utilized for heating. If a valve is included between the two vessels,the heat or cold production can be interrupted for any periods withoutloss of energy.

Zeolite is a general term for natural or synthetic stone like materialswhich consist of crystalline metal-alumo-silicates with a large internalsurface area of up to 1000 m²/g, strong electrostatic fields in thecrystal lattice and with a volumetric density of about 0.8 kg/dm³.Zeolites are useful as molecular sieves, as adsorbents, as catalysts incracking of hydrocarbons in the pretro-chemical industry, as a fillercomponent in paper production, as an ion exchange material indetergents, in adiabatic cooling or heating, fillers in cosmetics, andadditives in soaps.

Zeolites are tetrahedras consisting of four oxygen anions and onecentrally positioned silicon or aluminum cation. Zeolites are classifiedaccording to the various tetrahedral frameworks formed by these basicbuilding blocks. Aluminum and silicon atoms are positioned at junctionswhile oxygen atoms form bridges between tetrahedras. The difference inelectro-chemical charges between the aluminum and silicon atoms per onealuminum atom results in a non-compensated negative charge. The balanceis restored by metal cations which occupy preferred positions. Becauseof the strong local electrical dipole moment in the lattice framework,zeolites adsorb polar and non-polar molecules that will fit into theirspecific framework. This adsorption process is accompanied by release ofheat, the heat of adsorption.

Microencapsulating zeolites can provide advantages in terms of controlof rate of contact with water and control in rate of heating or asWheeler et al., describe prolonging the sensation of heating such as inan applied cosmetic or lotion. The microcapsule wall material can beselected to be selectively permeable, nonpermeable, porous, semi-porous,have osmotic character, water soluble, water disintegratable, or waterfracturable. With optionally a water permeable or a water soluble wallmaterial, the degree of water solubility or permeance can beadvantageously adapted to provide a desired rate of water contact withthe encapsulated solid hydrophilic material.

Although encapsulation of various materials is known in the art, a needpersists for techniques to coat solid hydrophilic core materials.Although rotary coaters and fluidized bed processes exist, suchprocesses tend to be coarse, throwing coating onto particles or meltblending particles as compared to coacervation, interfacial or solutiondeposition methods of capsule formation.

Where consistency of wall thickness, uniform deposition, engineering ofthe wall chemistry, control of release rates, control of chargecharacteristics, uniform layering, and the like properties areimportant, the techniques and compositions of the present inventionprovide a novel process and chemistry to achieve forming a population ofmicrocapsules with an ionic wall material at least partially surroundinga solid hydrophilic core material.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an illustration of one embodiment of microcapsules accordingto the invention.

SUMMARY OF THE INVENTION

The present invention discloses a process of forming a population ofmicrocapsules comprising particles of a solid hydrophilic core materialand a wall material at least partially surrounding the core material,the microcapsule population being formed by providing a solidhydrophilic core material; providing an oil continuous phase which islow boiling and preferably nonflammable, the oil continuous phasecomprising one or more hydrocarbons with chain length up to about 18carbons; forming a mixture by adding an oil soluble or dispersible amineacrylate or methacrylate; adding a multifunctional acrylate ormethacrylate monomer or oligomer; adding an acid and an initiator;optionally adding a surfactant; dispersing the mixture by subjecting themixture to agitation; heating the mixture for a time sufficient toenable the amine acrylate or methacrylate and the multifunctionalacrylate or methacrylate to form a cationic prepolymer; dispersing thesolid hydrophilic material in the oil continuous phase whereby thecationic prepolymer migrates to the solid hydrophilic material, therebyforming prepolymer adhered to the hydrophilic core materials; holdingthe temperature for a time sufficient to enable the cationic prepolymerto flow onto and coalesce into a continuous film surface coating on thehydrophilic core material; and heating for a time and temperaturesufficient to cross link the prepolymers. For purposes hereof, “holdingthe temperature” means that heating is continued and the temperaturemaintained within about 5° C. or even 10° C. plus or minus, preferablywithin 20° C. plus or minus, or even about 25° C. to 30° C. plus orminus the preceding heating step.

In a further embodiment, the present invention comprises a process forforming a population of microcapsules comprising a solid hydrophiliccore material and a wall material at least partially surrounding thecore material, the microcapsule population being formed by providingparticles of a solid hydrophilic core material; providing an oilcontinuous phase which is low boiling and preferably nonflammable, theoil continuous phase comprising one or more hydrocarbons with chainlength up to about 18 carbons; dividing the oil continuous phase intooil 1 and oil 2; dispersing into oil 1 an initiator; dispersing into oil2 a multifunctional acrylate or methacrylate monomer or oligomer, and anoil soluble or dispersible amine acrylate or methacrylate, and an acid;subjecting oil 1 to one or more heating steps; combining oil 1 and oil2; subjecting the combined oils to one or more heating steps, forming acationic wall prepolymer; forming a mixture by dispersing the solidhydrophilic material into the oil continuous phase and mixing for asufficient time to allow the wall prepolymer to migrate to and depositonto the solid hydrophilic core material particles; optionally adding asurfactant; holding the temperature for a time sufficient to enable thecationic prepolymer to flow onto and coalesce into a continuous filmsurface coating on the hydrophilic core material; and heating themixture for a time sufficient to cross-link the deposited prepolymercontinuous film on the surface of the particles.

In either of the above embodiments, preferably the acid and amineacrylate or methacrylate have a percent by weight as compared to weightof the wall material of from 0.1 to 10 or even 25 percent, and/or have amolar proportion of from 1.25/1 to about 1/1.25, or even 1.5/1 to about1/1.5.

The solid hydrophilic core material is optionally selected from thegroup consisting of anionic, cationic, or neutral but polar material.

Preferably in any of the embodiments disclosed herein the amine acrylateor methacrylate is selected from a monofunctional amine acrylate or amonofunctional amine methacrylate with a nitrogen content of 5% byweight or greater. Alternatively, the amine acrylate is selected fromthe group consisting of alkyl amino acrylate and alkylaminomethacrylatehaving a nitrogen content of 5% by weight or greater.

In yet a further embodiment, in the processes of the invention the acidcan be selected to be a carboxylic acid acrylate or carboxylic acidmethacrylate having a —COOH content of 20% or greater by weight.

In another embodiment, the present invention discloses a process offorming a population of microcapsules comprising a hydrophilic solidcore material and a wall material at least partially surrounding thecore material, the microcapsule population being formed by providingparticles of a solid hydrophilic core material; providing an oilcontinuous phase which is low boiling and preferably nonflammable, theoil continuous phase comprising one or more hydrocarbons with chainlength up to about 18 carbons; forming a mixture by adding an oilsoluble or dispersible acid acrylate or methacrylate; adding amultifunctional acrylate or methacrylate monomer or oligomer; adding abase and an initiator; optionally adding a surfactant; dispersing themixture by subjecting the mixture to high shear agitation; heating themixture for a time sufficient to enable the acid acrylate ormethacrylate and the multifunctional acrylate or methacrylate to form ananionic prepolymer; dispersing the solid hydrophilic material in the oilcontinuous phase whereby the anionic prepolymer migrates to and depositsonto a surface of the solid hydrophilic material, thereby formingprepolymer adhered to the surface of the hydrophilic core materialparticles; and heating for a time and temperature sufficient to crosslink the deposited prepolymer on the surface of the particles.

In a further embodiment the present invention discloses a process forforming a population of microcapsules comprising a solid hydrophiliccore material and a wall material at least partially surrounding thecore material, the microcapsule population being formed by providingparticles of a solid hydrophilic core material; providing an oilcontinuous phase which is low boiling and preferably nonflammable, theoil continuous phase comprising one or more hydrocarbons with chainlength up to about 18 carbons; dividing the oil continuous phase intooil 1 and oil 2; dispersing into oil 1 an initiator; dispersing into oil2 a multifunctional acrylate or methacrylate monomer or oligomer, and anoil soluble or dispersible acid acrylate or methacrylate, and a base;subjecting oil 1 to one or more heating steps; combining oil 1 an oil 2;subjecting the combined oils to one or more heating steps, forming ananionic wall prepolymer; forming a mixture by dispersing the solidhydrophilic material into the oil continuous phase and mixing for a timesufficient to allow the wall prepolymer to migrate to and deposit onto asurface of the solid hydrophilic core material particles; holding thetemperature for a time sufficient to enable the anionic prepolymer toflow onto the coalesce into a continuous film surface coating on thehydrophilic core material; optionally adding a surfactant, and heatingthe mixture for a time sufficient to cross-link the deposited prepolymercontinuous film surface coating on the particles.

Preferably in the foregoing embodiment, hydrocarbons of the oilcontinuous phase are esters.

Preferably the wall material is selected to be a water permeable,partially water permeable, water soluble, partially water soluble, waterfracturable, water disintegratable, semi-porous or an osmotic material.

The oil continuous phase can comprise in addition sucrose octylstearate, a polysaccharide, polyethylene glycol, esters of polyethyleneglycol, esterified polyol, saccharide ester, or wax.

Optionally, if desired, a water soluble polymer can be added in additionto the multifunctional acrylate.

In the foregoing embodiments forming or crosslinking the prepolymers canbe accomplished by heating the mixture or exposing the mixture toactinic radiation or both.

In the above embodiments the solid hydrophilic core material can beselected from the group consisting of anionic, cationic, or neutral butpolar material. Preferably in the embodiments with base and acidacrylate or acid methacrylate, the base and acid acrylate or acidmethacrylate have a percent by weight as compared to weight of the wallmaterial of from 0.1 to 10 percent, or even from 0.1 to 20%, or evenfrom 0.1 to 25%.

Optionally when base is employed in the embodiments, the base can be anamine acrylate or methacrylate.

In a further embodiment the invention discloses a population ofmicrocapsules comprising a solid hydrophilic core material; a wallmaterial at least partially surrounding the core material, themicrocapsule wall material comprising a reaction product from within anoil continuous phase of i) an oil soluble or dispersible amine acrylateor methacrylate with ii) a multifunctional acrylate or methacrylatemonomer or oligomer, and iii) a soluble acid and an initiator, whereini), ii) and iii) are first dispersed in an oil continuous phase andsubjected to one or more heating steps followed by the step ofintroduction of the solid core; wherein the oil continuous phase is lowboiling and preferably nonflammable, the oil continuous phase comprisingone or more hydrocarbons with chain length up to about 18 carbons;wherein the soluble acid and the amine acrylate are in a molarproportion from 3:1 to 1:3 and together have a percent by weight ascompared to the weight of the wall material of from 0.1 to 20%, from 0.1to 25%, or even from 0.1 to about 35%, whereby the reaction productresults in the formation of a population of microcapsules having ahydrophobic microcapsule wall material at least partially surrounding asolid hydrophilic core material.

In a yet further embodiment the invention describes a population ofmicrocapsules comprising a solid hydrophilic core material; a wallmaterial at least partially surrounding the core material, themicrocapsule wall material comprising a reaction product from within anoil continuous phase of i) an oil soluble or dispersible acid acrylateor methacrylate with ii) a multifunctional acrylate or methacrylatemonomer or oligomer, and iii) a soluble base and an initiator, whereini), ii) and iii) are first dispersed in an oil continuous phase andsubjected to one or more heating steps followed by the step ofintroduction of the solid core; wherein the oil continuous phase is lowboiling and preferably nonflammable, the oil continuous phase comprisingone or more hydrocarbons with chain length up to about 18 carbons;wherein the soluble base and the acid acrylate are in a molar proportionfrom 3:1 to 1:3 and together have a percent by weight as compared to theweight of the wall material of from 0.1 to 20%, whereby the reactionproduct results in the formation of a population of microcapsules havinga hydrophobic microcapsule wall material at least partially surroundinga solid hydrophilic core material.

DETAILED DESCRIPTION

The present invention discloses a population of microcapsules comprisingsolid hydrophilic core material, selected to be anionic, cationic orneutral but polar; a wall material at least partially surrounding thecore material, the microcapsule wall material comprising a reactionproduct from within an oil continuous phase of i) an oil soluble ordispersible amine acrylate or methacrylate with ii) a multifunctionalacrylate or methacrylate monomer or oligomer, and iii) a soluble acidand an initiator, wherein i) ii) and iii) are first dispersed in an oilcontinuous phase and mixed for a sufficient time to form a prepolymerwhich is allowed sufficient time to migrate to and deposit onto thesolid hydrophilic core material.

The oil continuous phase is low boiling and preferably nonflammable, theoil continuous phase preferably comprises one or more hydrocarbons,preferably esters with chain length up to about 18 carbons. The solubleacid and the amine acrylate are preferably in a molar proportion from3:1 to 1:3 and together preferably have a percent by weight as comparedto the weight of the wall material of from 0.1 to 20%.

The particles of solid hydrophilic core material can be provided asparticulates or precipitated from the continuous phase.

Multifunctional acrylate or methacrylate monomers or oligomers caninclude di-; tri-; tetra- penta-; hexa-; hepta-; or octa-functionalacrylate esters, methacrylate esters and multi-functional polyurethaneacrylate esters and epoxy acrylates stable in the presence of initiator.Monomers shall be understood as including oligomers thereof. Optionally,an inhibitor such as hydroquinone can be added to the monomer andinitiator blend in the capsules to prevent premature polymerization.

Useful monomers in the invention are di- and poly-functional acrylateesters, difunctional (meth)acrylate esters, polyfunctional(meth)acrylate esters, difunctional urethane acrylate esters,polyfunctional urethane acrylate esters and polyfunctional anddifunctional epoxy acrylate monomers and oligomers used alone or incombination as blends. In alternate embodiments, optionally, the di- andpolyfunctional acrylates, methacrylates, urethane acrylates, and epoxyacrylates are further blended with monofunctional acrylates,methacrylates, urethane acrylates and epoxy acrylates.

In an aspect of the invention multi-functional acrylate or methacrylatemonomers or oligomers preferably are selected to have a Tg>60° C., inone aspect greater than 70° C., and in another aspect greater than 80°C., and can include by way of illustration and not limitation, allylmethacrylate; triethylene glycol dimethacrylate; ethylene glycoldimethacrylate, diethylene glycol dimethacrylate, aliphatic or aromaticurethane diacrylates, difunctional urethane acrylates, ethoxylatedaliphatic difunctional urethane methacrylates, aliphatic or aromaticurethane dimethacrylates, epoxy acrylates, epoxymethacrylates;tetraethylene glycol dimethacrylate; polyethylene glycol dimethacrylate;1,3 butylene glycol diacrylate; 1,4-butanediol dimethacrylate;1,4-butaneidiol diacrylate; diethylene glycol diacrylate; 1,6 hexanedioldiacrylate; 1,6 hexanediol dimethacrylate; neopentyl glycol diacrylate;polyethylene glycol diacrylate; tetraethylene glycol diacrylate;triethylene glycol diacrylate; 1,3 butylene glycol dimethacrylate;tripropylene glycol diacrylate; ethoxylated bisphenol diacrylate;ethoxylated bisphenol dimethylacrylate; dipropylene glycol diacrylate;alkoxylated hexanediol diacrylate; alkoxylated cyclohexane dimethanoldiacrylate; propoxylated neopentyl glycol diacrylate, trimethylolpropanetrimethacrylate; trimethylolpropane triacrylate, pentaerythritoltriacrylate, ethoxylated trimethylolpropane triacrylate, propoxylatedtrimethylolpropane triacrylate, propoxylated glyceryl triacrylate,ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate,ethoxylated pentaerythritol tetraacrylate.

Useful amines can include by way of illustration and not limitationamine modified vinyl monomers including amine modified acrylate ormethacrylates such as mono or diacrylate amines, mono or dimethacrylateamines, amine modified polyetheracrylates and amine modifiedpolyethermethacrylates, aminoalkyl acrylates or aminoalkyl methacrylate.Preferred are monofunctional amine acrylates or amine methacrylates suchas aminoalkylacrylates or aminoalkylmethacrylates with a nitrogencontent of 5% by weight or greater.

The amines can include primary, secondary or tertiary amines and caninclude tertiary butyl aminoethylmethacrylate, diethylaminoethylmethacrylate, or dimethylaminoethyl methacrylate. Water soluble basespreferably include typical bases such as NaOH or KOH, but can includeother typical oxides and hydroxides of metals and ammonia. The baseoptionally can comprise monofunctional amine acrylate or monofunctionalamine methacrylate with a nitrogen content by weight of 5% or greater.Examples include alkylaminoacrylate and alkylaminomethacrylates.

The oil soluble acid is preferably an organic acid. The organic acid canbe selected from various acids such as carboxy acids, with monoalkylmaleates such as monomethyl, monoethyl or monobutyl maleate beingpreferred, with monobutyl maleate being most preferred. Other preferredorganic acids include beta-carboxyethyl acrylate. Yet other organicacids that can be usefully employed in the invention include, organicsulfonic acids such as alkyl benzene sulfonic acid, more particularlylinear alkyl benzene sulfonic acid, tridecylbenzene sulfonic acid, moreparticularly linear trialkyl benzene sulfonic acid such as lineartridecyl benzene sulfonic acid, alkyldiphenyloxide sulfonic acid,preferably dodecyl diphenyl oxidedisulfonic acid, more particularlybranched C12 diphenyl oxide disulfonic acid, alkylbenzene sulfonic acid,more particularly, dodecyl benzene sulfonic acid, dialkyl naphthalenedisulfonic acid, more particularly dinonylnaphthalene disulfonic acid,4-hydrozino benzene sulfonic acid acrylic acid, methacrylic acid, andthe like. Desirably the organic acid is selected to be dispersible inthe oil phase and sparingly soluble in the water phase. The organic acidis used as 0.1 to 20%, preferably 3 to 10.0%, and more preferably5.0-7.0% by weight based on percentage of total wall. Useful acids alsoinclude standard strong acids such as HCl, H₂SO₄, and H₃PO₄. Acids arehydrogen ion source materials and can include mineral acids, solutionsof hydrogen halides, and various materials that increase theconcentration of hydrogen ions in solution. Optionally the acid can becarboxylic acid acrylate or carboxylic acid methacrylate having a —COOHcontent of 20% or greater by weight. Bases when employed includealkaline materials and can include materials that donate electrons orhydroxide ions or accept protons such as alkaline hydroxides includingNaOH, NH4OH or KOH.

Excluding solvent, the primary, secondary or tertiary amine acrylate ormethacrylate and the multi-functional acrylate or methacrylate monomersare used in a relative weight ratio of from about 0.1:99.9 to about10:90 preferably from about 0.5:99.5 to about 5:95, and most preferably1:99 to about 3:97.

Low molecular weight secondary or tertiary amines can be also employedas the amine provided they are oil soluble or dispersible.

Similarly in embodiments based on acid acrylate or methacrylate withmultifunctional acrylates or methacrylate monomer, the acid acrylate ormethacrylate and the multifunctional acrylate or methacrylate are in arelative weight ratio of from 0.1:99.9 to about 10:90 preferably fromabout 0.5:99.5 to about 5:95, and most preferably 1:99 to about 3:97.

The initiators are energy activated meaning generating free radicalswhen subjected to heat or other energy input. Preferred initiatorsinclude peroxy initiators, azo initiators, peroxides, and compounds suchas 2,2′-azobismethylbutyronitrile, dibenzoyl peroxide. Moreparticularly, and without limitation the free radical initiator can beselected from the group of initiators comprising an azo or peroxyinitiator, such as peroxide, dialkyl peroxide, alkyl peroxide,peroxyester, peroxycarbonate, peroxyketone and peroxydicarbonate,2,2′-azobis(isobutylnitrile), 2,2′-azobis(2,4-dimethylpentanenitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-methylpropanenitrile), 2,2′-azobis(methylbutyronitrile),1,1′-azobis(cyclohexanecarbonitrile), 1,1′-azobis(cyanocyclohexane),benzoyl peroxide, decanoyl peroxide; lauroyl peroxide; benzoyl peroxide,di(n-propyl)peroxydicarbonate, di(sec-butyl)peroxydicarbonate,di(2-ethylhexyl)peroxydicarbonate, 1,1-dimethyl-3-hydroxybutylperoxyneodecanoate, α-cumyl peroxyneoheptanoate, t-amylperoxyneodecanoate, t-butyl peroxyneodecanoate, t-amyl peroxypivalate,t-butyl peroxypivalate, 2,5-dimethyl 2,5-di(2-ethylhexanoylperoxy)hexane, t-amyl peroxy-2-ethyl-hexanoate, t-butylperoxy-2-ethylhexanoate, t-butyl peroxyacetate, di-t-amyl peroxyacetate,t-butyl peroxide, di-t-amyl peroxide,2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3, cumene hydroperoxide,1,1-di-(t-butylperoxy)-3,3,5-trimethyl-cyclohexane,1,1-di-(t-butylperoxy)-cyclohexane, 1,1-di-(t-amylperoxy)-cyclohexane,ethyl-3,3-di-(t-butylperoxy)-butyrate, t-amyl perbenzoate, t-butylperbenzoate, ethyl 3,3-di-(t-amylperoxy)-butyrate, and the like. Blendsof initiators can also be employed. Initiators are availablecommercially, such as Vazo initiators, which typically indicate adecomposition temperature for the initiator. Preferably the initiator isselected to have a decomposition point of about 50° C. or higher.Usefully multiple initiators are employed, either as a blend in the oilphase, or in either of the oil or water phases. Preferably initiatorsare selected to stagger the decomposition temperatures at the varioussteps, pre-polymerization, wall formation and hardening or polymerizingof the capsule wall material. For example, a first initiator in the oilphase can decompose at 55° C., to promote prepolymer formation, a secondcan decompose at 60° C. to aid forming the wall material. Optionally athird initiator can decompose at 65° C. to facilitate polymerization ofthe capsule wall material. The total amount of initiator can betypically as low as 0.1 weight percent or as high as 10 weight percent.

The oil continuous phase or oil phase used interchangeably for purposeshereof can be selected from hydrocarbons, more particularly hydrocarbonsolvents and the solvents can include by way of illustration and notlimitation, ethyldiphenylmethane, butyl biphenyl ethane, benzylxylene,alkyl biphenyls such as propylbiphenyl and butylbiphenyl, dialkylphthalates e.g. dibutyl phthalate, dioctylphthalate, dinonyl phthalateand ditridecylphthalate; 2,2,4-trimethyl-1,3-pentanediol diisobutyrate,alkyl benzenes such as dodecyl benzene; alkyl or aralkyl benzoates suchas benzyl benzoate; diaryl ethers, di(aralkyl)ethers and aryl aralkylethers, ethers such as diphenyl ether, dibenzyl ether and phenyl benzylether, liquid higher alkyl ketones (having at least 9 carbon atoms),alkyl or aralky benzoates, e.g., benzyl benzoate, alkylated naphthalenessuch as dipropylnaphthalene, partially hydrogenated terphenyls;high-boiling straight or branched chain hydrocarbons, alkarylhydrocarbons such as toluene, vegetable oils such as canola oil, soybeanoil, corn oil, sunflower oil, or cottonseed oil, methyl esters of fattyacids derived from transesterification of canola oil, soybean oil,cottonseed oil, corn oil, sunflower oil, pine oil, lemon oil, olive oil,or methyl ester of oleic acid, vegetable oils, esters of vegetable oils,e.g. soybean methyl ester, straight chain saturated paraffinic aliphatichydrocarbons of from 10 to 13 carbons. Mixtures of the above can also beemployed. Common diluents such as straight chain hydrocarbons can alsobe blended with the solvents, or blend of solvents. The solvent isselected on the basis of hydrophobicity and ability to disperse orsolvate the amine modified vinyl monomer and the multi-functionalacrylate or methacrylate monomer or oligomer, and/or the acid acrylate.

Preferably the oil continuous phase comprises one or more esters withchain length of up to about 18 carbons. An example of such an oilcontinuous phase material is isoamylbenzoate, capric triglyceride,caprylic triglyceride or blends thereof.

Other preferred oil continuous phase material include C₁₆ to C₁₈ soyesters.

Lower carbon length esters can also be employed however care must betaken such as with C₅ to C₈ esters to minimize flammability such asusing a nitrogen blanket.

In a preferred process the oil continuous phase is divided into twooils, oil 1 and oil 2. The initiator is dispersed in oil 1. Oil 1 andoil 2 can be the same or different. Preferably they are divided portionsof the same oil. An initiator is dispersed in oil 1. Into oil 2 amultifunctional acrylate or methacrylate monomer or oligomer, an oilsoluble amine acrylate or methacrylate and an acid is dispersed.Optionally the oil soluble amine acrylate or methacrylate is substitutedwith an acid acrylate or methacrylate and base. Oil 1 and oil 2 arecombined. A solid hydrophilic material is dispersed into any of oil 1,oil 2 or the combined oils. “Dispersing the solid hydrophilic materialinto the oil continuous phase” is intended to encompass any or all ofthese variations.

Optionally a surfactant can be added, selected to have less charge thanthe solid hydrophilic material.

Also optionally the oil continuous phase comprises or is blended with asecond material that influences properties of the finished wall materialof the microcapsules. Such materials can change rheology, influencepermeability, rate of disintegration, or porosity of the wall. Suchoptional materials for the oil continuous phase include sucrose octylstearate, polysaccharides, polyethylene glycol, esters of polyethyleneglycol, esterified polyol, saccharide ester or wax. Advantageously, acertain portion of such optional oil phase materials are carried withand incorporated in the microcapsule wall surrounding the solidhydrophilic core.

After the wall forming materials and solid hydrophilic core material aredispersed in the oil or oils of the continuous phase and/or oil 1 andoil 2 are combined, along with acid or base respectively depending onwhether amine acrylate or methacrylate or acid acrylate or methacrylateis selected as wall forming materials, wall pre-reaction can be carriedout by heat or light depending on the initiator employed. Optionally,oil 1 can be heated or subjected to light, depending on the initiatorsystem used, to create a population of free radicals, prior to combiningthe two oil solutions for wall pre-reaction.

After wall pre-reaction, the oil solution is milled and heated or UVexposed for a sufficient time to allow wall deposition to proceed. Thisprocess is further illustrated and explained in the examples.

In an alternative embodiment, in the first composition, the initiatorcan be an energy-activated initiator, relying in place of heat or inaddition to heat, on light such as a UV or light induced or electronbeam induced free radical. Optionally a visible light induced freeradical generator could also be used. This dispersion is then subjectedto UV light to generate free radicals and initiate polymerization.Depending on the type of initiator or initiators, the dispersion issubjected to UV light and/or heated (as appropriate to the initiator orinitiators) to generate free radicals. The term energy activated isintended to encompass heat, or light, UV or visible or infrared, orelectron beam activation, without limitation.

As polymerization progresses induced by heat or light, microcapsule wallmaterial prepolymer forms and is drawn to the interface of the solidhydrophilic particle and oil phases. The core material can be selectedto be anionic, cationic, or neutral but polar. Preferably the prepolymerand wall material is oppositely charged or polar to facilitate migrationto the hydrophilic core material. UV exposure and/or heating steps canbe used to further polymerize or harden the formed wall material.

UV initiators can include ketone compounds and can include benzophenone;acetophenone; benzil; benzaldehyde; o-chlorobenzaldehyde; xanthone;thioxanthone; 9,10-anthraquinone; 1-hydroxycyclohexyl phenyl ketone;2,2-diethoxyacetophenone; dimethoxyphenylacetophenone; methyldiethanolamine; dimethylaminobenzoate;2-hydroxy-2-methyl-1-phenylpropane-1-one; 2,2-di-sec-butoxyacetophenone;2,2-dimethoxy-1,2-diphenylethan-1-one; dimethoxyketal; and phenylglyoxal. 2,2′-diethoxyacetophenone; hydroxycyclohexyl phenyl ketone;alpha-hydroxyketones; alpha-amino-ketones; alpha and beta naphthylcarbonyl compounds; benzoin ethers such as benzoin methyl ether; benzyl;benzil ketals such as benzil dimethyl ketal; acetophenone; fluorenone,2-hydroxy-2-methyl-1-phenylpropan-1-one. UV initiators of this kind areavailable commercially, e.g., IRGACURE 184™ or DEROCURE 1173™ from Ciba.Thermal initiators are available from DuPont. The fraction of the photoinitiator in any of the water or oil phase is approximately from about0.1 to 10%, preferably 0.25 to about 6% by weight, more preferably 0.5to 2.5 weight percent. Similar weight percent ranges can also be appliedto the thermal initiators.

UV initiators can be included in substitution as an alternate initiatorsystem (for any heating step or steps of the encapsulation process, oras an additional initiator system). In a yet further embodiment, forspecialized microencapsulation processes, the use of initiators, e.g.,thioxanthones, phosphine oxides, metallocenes, tertiary aminobenzenes ortertiary aminobenzophenones, which break down into free radicals onexposure to visible light is effectively used. Such microencapsulationsystems however typically require special handling of the system toprevent premature polymerization or oligomerization by appropriatecontrol of lighting conditions.

This produces an initiator system for polymerization or oligomerizationusing a dual cure method or optional thermal or optional light oroptional UV initiated method by appropriate selection of initiator andinitiation method or methods. In an alternative embodiment of theinvention, azo compounds that can be excited or split by UV light orhigh-energy radiation are used alone or in combination with thermal freeradical initiators. In a yet alternative embodiment, the combination ofthermal and UV initiators is formed only by azo compounds.

For light activated microencapsulation, the use of UV initiators arepreferred, or a combination of UV initiators and thermal free radicalinitiators. This combination can impart considerable versatility to themicroencapsulation steps of the process where any step or steps of themicroencapsulation process then can be initiated either by appropriateselection of an initiator decomposing at specific temperatures ordecomposing under specific light conditions. This versatility in theselection of initiators also allows sufficient flexibility in theencapsulation system to customize encapsulation conditions for a givencore material. For example, highly volatile or heat-sensitive materialsmay be more effectively encapsulated with minimal heating, through theuse of energy-cure methods.

In a yet further embodiment, with appropriate selection of monomers andinitiators, the respective monomers in the process can be polymerized oroligomerized using some suitable means such as heat (used with thermalinitiators) or UV light (for use with UV initiators), or electron beam.When replacing the UV radiation with electron beam, the addition ofinitiators is not absolutely essential or amounts employed can bereduced. Options for individual initiation steps of the encapsulationprocess include the freedom to use in replacement of any heating step,the use of visible light with suitable initiators, the use of UV lightwith suitable UV initiators, or ionizing radiation (e.g. electron beamor gamma ray) without initiators or reduced amounts of initiator.

UV initiators may be selected from those organic chemical compoundsconventionally employed to promote UV-initiated formation of radicals. Apreferred UV initiator is 1-hydroxycyclohexyl phenyl ketone because ofthe rapidity with which it generates free radicals when exposed to UVradiation. Mixtures of UV initiators or mixtures with thermal initiatorsmay also be used. This is often desirable because it provides moreefficient production of radicals in certain cases. In general, the UVinitiator will be present in an amount of 0.1 to 10.0 weight percent inany of the water or oil phases, based on the total weight of allconstituents. However, it is preferable to use between 0.25-2.5 weightpercent UV initiator, most preferably 0.5-1.0 weight percent UVinitiator, based on total weight.

The amount of each initiator, thermal, UV or light, that is employed canvary, and is dependent upon factors such as the monomer or oligomermaterial. Typically, the amount of initiator ranges from about 0.1 toabout 6 percent, and often about 1 to about 3 percent, based on theweight of all constituents.

A process of microencapsulation based on UV curing has the advantage ofallowing the encapsulation of highly volatile or heat sensitive corematerials. UV curable wall systems can have lower energy usage thananalogous thermal-cured systems. In certain aspects, a UV-curable systemhas the potential of increased throughput and efficiency through use ofphoto initiation.

Looking now at FIG. 1, reactor 4 is provided with impeller 3.Optionally, the reactor can be transparent to permit light passage. UVlight source 5 is provided and ΔQ indicates a quantity of heat appliedto the reactor slurry. The microcapsule is depicted in exaggerated sizeto help in illustration of the process. The microcapsule population isformed by providing anionic solid hydrophilic material 2. In analternative embodiment charges can be the reverse by selecting acationic, or even nonionic solid hydrophilic core. If nonionic, treatingwith surfactant may be necessary to drive wall material to the particle.Solid hydrophilic material 2 is dispersed and comminuted into thecontinuous phase oil shown in FIG. 1 as isoamyl benzoate along with aninitiator, and preferably a thermal or actinic radiation free radicalgenerator.

An amine acrylate and acid, when the solid hydrophilic particle isselected as anionic; or in the case when the solid hydrophilic particleis cationic, an acid acrylate and base; are added to and dispersed intothe continuous phase oil. Optionally some surfactant can be added alongwith multifunctional acrylate and the solid hydrophilic core particlesof desired size. The mixture is further milled if desired and comminutedto desired particle size. UV light radiation such as light source 5 isprovided and/or heat quantity 6. In thermally initiated systems a ΔQheat quantity may be sufficient. ΔQ can be provided in increments topre-react the polymers and following acid (or base addition) to cure orharden the polymers or pre-polymers as they migrate to the surface ofsolid hydrophilic particle 2 to form wall material 1. In this embodimentwall material 1 is depicted as cationic or carrying a level of positivecharge. In an alternative embodiment the charges can be reversed withthe wall material being anionic and the solid hydrophilic particle beingcationic.

Most solid hydrophilic particles will typically exhibit anioniccharacter. Cationic hydrophilic particles include aminofunctionalpolymers or resins.

The process and microcapsules according to the invention enableprotection of water sensitive materials since the capsules do not comeinto contact with water during encapsulation. The capsule wall can alsoprovide additional structure to slow release or until laterdisintegration. The capsule wall can also delay release as a function ofwall permeability or provide for release by fracture, pressure,friction, heat, shock, sonics, scraping, and like mechanisms. Watersoluble or partially water soluble capsule wall can provide release bydissolution. By release it is meant that the solid hydrophilic particlethat is coated is able to be contacted by water, can contact the water,or can diffuse to the water, for example if the solid hydrophilicmaterial is a gel-like material. Examples of core materials-usefullyencapsulated by the microcapsules and process of the invention includeabsorbents, adsorbents, sugars, aluminosilicates, molecular sievematerials, zeolites, and the like.

Layering of multiple layers onto the solid hydrophilic particles is alsopossible by repeated dispersion steps according to the invention. Insuch fashion hydrophilic and/or relative hydrophobic character can becustomized in each layer to provide a membrane effect and/or to controlrelative observed charge on the external surface of the solidhydrophilic particle before encapsulation or to a customizedconfiguration and charge after encapsulation.

The process of invention can be effectively used to encapsulate varioussolid hydrophilic materials including dessicated porous glasses,polyhedral alumina or titania crystals, calcined silicas and silicateswith pores with pores in the micrometer range, 0.1 to 110 microns, andpreferably 0.25 to 20 micron pore size, ordered polymers, aluminosilicates, a variety of microporous materials including metal silicas,zeolites, ceramics, alumina, titania, and even dessicated powderedsteels. Other solid hydrophilic materials could include sugars, fumaricacid, calcium hydroxide, other solid carboxylic acids or solid bases,herbicides, pesticides, algaecides, fungicides, polysaccharides,dessicated microporous polymeric materials such as polymeric beads,laser inradiated polyimides or polycarbonates, nylon, polyvinylideneflouride, cellulose acetate/nitrate, polysulfone, polypropylene,polyamide. Many of these types of materials and zeolites for examplehave an affinity for absorbing water. Encapsulation can be effectivelyutilized to preserve a dessicated condition until desired. Thesematerials often exothermally release heat upon absorption of water.Encapsulation can be useful to control the rate of water uptake and/orcontrol the rate of heat diffusion. Silicas and silicates are known forpurposes of forming molecular sieves and other materials with a uniformpore structure. The uniformity of size of the pore structure of themembrane often is more important to the end use generally than theparticular method of forming, molding, dissolving, etching, lasering,layering, calcining or other technique used to fashion the solidhydrophilic material.

The solid hydrophilic particles can be conditioned or emulsificationenhanced either by adding a surfactant in the emulsification step or byconditioning the solid hydrophilic material by modifying the solidhydrophilic particles' relative hydrophillicity or altering itshydrophobicity.

For example, when aluminum silicas are used, it is possible to enhancethe hydrophillicity of the surface on the external side of the particle.An optional acid soak, though not required, may be applied with aluminumsilicates to enhance hydrophillicity. Other treatments can includeapplying a sol gel of fluoralkoxides of elements of group IIA in anorganic solvent, followed by hydrolysing and washing away of any solublesalts. Dessicating following such treatments may be needed beforeemulsification in the process of the invention.

Surfactants useful in the invention can also be used as a treatment ofthe particles prior to emulsification and prior to dispersion in thecontinuous phase oil. Hydrophillic character can be increased bytreating with surfactants such as sodium dodecyl sulfate or sodiumdodecylbenzene sulfate. For modifying relative hydrophobicity, cationicsurfactants such as cetyl trimethylammonium bromide can be used.Hydrophobicizing glass membrane particles can be accomplished throughchemical absorption on the membrane of a hydrophobic film such asdimethylpolysiloxane, silicone oils, methyltrimethylsilane,isopropyltristearyltitanote and the like as taught in Japanese Laid OpenPatent Application (Kokai) No. 5[1993]-240 Application No.3[1991]-153126 by Osaka Glass Co. (“Manufacture of Inorganic UniformMicrospheres.” Silanation advantageously can produce more long lastinghydrophobic conditioning.

Encapsulation of Hydrophilic Solid with Acrylate-Wall

EXAMPLE 1

Oil 1: 450 grams isoamyl benzoate Oil 2: 50 grams isoamylbenzoate 1 gVazo-52 0.5 g conc. HCl 0.5 g Vazo-67 10 g SR 206 ethyleneglycoldimethacrylate 1 g TBAEMA t-butylaminoethyl methacrylate Core: 100 gcalcined clay

Oil 1 added to steel jacketed reactor with N2 blanket on at 300 cc/minand mixing at 1500 rpm (4-tip flat mill). Oil heated from 35° C. to 75°C. in 45 minutes and held at 75° C. for 35 minutes. Oil 1 is cooled to55° C. in 75 minutes. Oil 2 is added at 55° C., and combined oils mixedat 55° C. for 75 minutes. 100 g Ansilex clay added with mixing at 1000rpm. Rpm is increased to 3000 for one hour of milling, then rpmdecreased to 2500 for duration of heating cycle. The batch was heated to75° C. and held at 75° C. for 4 hours and 90° C. for 8 hours. While notbound by theory, wall deposition would occur during the 55° C. heatingstep while continuing in the 75° C. heating step. Wall coalescence andsurface coating occurs primarily in the 75° C. heating step along theearly stages of cross-linking. The 90° C. heating step cross-links thedeposited and coalesced polymeric particle coating. The resultant slurryis fluid with discrete encapsulation particles observable.

EXAMPLE 2

The encapsulation process according to Example 1, except using 2 gTMAEMA, and 100 g powdered sugar for the core. The resultant slurry isfluid with discrete encapsulation particles observable.

EXAMPLE 3

Oil 1: 150 grams caprylic/capric Oil 2: 50 g caprylic/caprictriglyceride triglyceride 1 g Vazo-52 0.5 g conc. HCl 0.5 g Vazo-67 10 gCN975 Urethane acrylate oligomer 1 g TBAEMA Core: 100 g fumaric acid

The process of Example 1 was followed to prepare microcapsules with thecorresponding substitutions in the ingredients noted above.

EXAMPLE 4

The process according to Example 1, was followed except 50 g calciumhydroxide is used for the core.

EXAMPLE 5

Oil 1: 200 grams isoamyl benzoate Oil 2: 50 grams isoamyl benzoate 0.5 gVazo-52 0.5 g TBAEMA 0.5 g Beta-C 10 g CN975 Core: 50 g powdered sugar

Oil 1 is added to a 35° C. glass jacketed reactor with a nitrogenblanket on at 100 cc/minute and with mixing at 400 rpm with a 1.5″propeller. The oil is heated to 75° C. in 45 minutes, hold at 75° C. for35 minutes, and cool to 55° C. in 75 minutes. Oil 2 is added and thecombined oils are held at 55° C. for 70 minutes then cooled to 25° C. in75 minutes. The core is added at 25° C. and is mixed at 500 rpm. Aphoto-initiator (Irgacure 651, 0.5 g) is added 85 minutes after the coreaddition, and a UV light is applied 90 minutes after the core addition.The UV light is applied for 8 hours, and results in a low viscosityencapsulated solid suspension.

Unless otherwise indicated, all measurements herein are on the basis ofweight and in the metric system. All references cited herein areexpressly incorporated herein by reference.

The abbreviations correspond to the following materials:

Company/City SR206 Sartomer Company, Exton, PA Ethyleneglycoldimethacrylate CN975 Sartomer Company, Exton, PA Hexafunctional AromaticUrethane Acrylate Oligomer TBAEMA Tertiarybutyl Aminoethyl MethacrylateVazo-52 DuPont, Wilmington, DE 2,2′-Azobis (2,4-Dimethylvaleronitrile)Vazo-67 DuPont, Wilmington, DE 2,2′-Azobis (2-Methylbutyronitrile)Vazo-68WSP DuPont, Wilmington, DE 4,4′-Azobis (4-Cyanovaleric Acid)Irgacure 651 CIBA, Tarrytown, NY 2,2-Dimethoxy-1,2-Diphenylethan-1-oneDarocure 1173 CIBA, Tarrytown, NY2-Hydroxy-2-Methyl-1-Phenyl-Propane-1-one IAB isoamyl benzoate Captex355 ABITEC Corporation, Columbus, OH Caprylic/Capric Triglyceride Beta-CBimax, Glen Rock, PA Beta-carboxyethyl acrylate Irgacure 651 CIBA,Tarrytown, NY 2,2-Dimethoxy-1,2-Diphenylethan-1-one

All documents cited in the specification herein are, in relevant part,incorporated herein by reference for all jurisdictions in which suchincorporation is permitted. The citation of any publication is for itsdisclosure prior to the filing date and should not be construed as anadmission that such publication is prior art or that the presentinvention is not entitled to antedate such publication by virtue ofprior invention. To the extent that any meaning or definition of a termin this document conflicts with any meaning or definition of the sameterm in a document incorporated by reference, the meaning or definitionassigned to that term in this document shall govern.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm”.

Uses of singular terms such as “a,” “an,” are intended to cover both thesingular and the plural, unless otherwise indicated herein or clearlycontradicted by context. The terms “comprising,” “having,” “including,”and “containing” are to be construed as open-ended terms. Anydescription of certain embodiments as “preferred” embodiments, and otherrecitation of embodiments, features, or ranges as being preferred, orsuggestion that such are preferred, is not deemed to be limiting. Allmethods described herein can be performed in any suitable order unlessotherwise indicated herein or otherwise clearly contradicted by context.The use of any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended to illuminate the invention and does notpose a limitation on the scope of the invention. No unclaimed languageshould be deemed to limit the invention in scope. Any statements orsuggestions herein that certain features constitute a component of theclaimed invention are not intended to be limiting unless reflected inthe appended claims.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A process of forming a population ofmicrocapsules comprising a solid hydrophilic core material and a wallmaterial at least partially surrounding the core material, themicrocapsule population being formed by: providing particles of a solidhydrophilic core material; providing an oil continuous phase which islow boiling, the oil continuous phase comprising esters or one or morehydrocarbons with chain length up to about 18 carbons; forming a mixtureby: adding an oil soluble or dispersible amine acrylate or methacrylate;adding a multifunctional acrylate or methacrylate monomer or oligomer;adding an acid and an initiator; optionally adding a surfactant;dispersing the mixture in the continuous phase by subjecting the mixtureto agitation; heating the mixture for a time sufficient to enable theamine acrylate or methacrylate and the multifunctional acrylate ormethacrylate to form a cationic prepolymer; dispersing the solidhydrophilic material in the oil continuous phase whereby the cationicprepolymer migrates to the solid hydrophilic material, thereby formingprepolymer adhered to the hydrophilic core materials; holding thetemperature for a time sufficient to enable the cationic prepolymer toflow onto and coalesce into a continuous film surface coating on thehydrophilic core material; heating for a time and temperature sufficientto cross link the prepolymer continuous film surface coating on theparticles.
 2. The process of forming a population of microcapsulesaccording to claim 1 wherein the acid and the amine acrylate ormethacrylate have a percent by weight as compared to weight of the wematerial of from 0.1 to 25 percent.
 3. The process of forming apopulation of microcapsules according to claim 1 wherein the weightratio of the amine to the multifunctional acrylate or methacrylate isfrom 0.1:99.9 to 10:90.
 4. The process of forming a population ofmicrocapsules according to claim 1 wherein the acid and the amineacrylate or methacrylate have a molar proportion of from 1.5/1 to about1/1.5.
 5. The process of forming a population of microcapsules accordingto claim 1 wherein the solid hydrophilic core material is selected fromthe group consisting of anionic, cationic, or neutral but polarmaterial.
 6. The process of forming a population of microcapsulesaccording to claim 1 wherein the amine acrylate or methacrylate isselected from a monofunctional amine acrylate or a monofunctional aminemethacrylate with a nitrogen content of 5% by weight or greater.
 7. Theprocess of forming a population of microcapsules according to claim 1wherein the amine acrylate is selected from the group consisting ofalkyl amino acrylate and alkylaminomethacrylate having a nitrogencontent of 5% by weight or greater.
 8. The process of forming apopulation of microcapsules according to claim 1 wherein the acid is acarboxylic acid acrylate or carboxylic acid methacrylate having a —COOHcontent of 20% or greater by weight.
 9. The process according to claim 1wherein the wail material is selected to be a water permeable, partiallywater permeable, water soluble, partially water soluble, waterfracturable, water disintegratable, semi-porous or an osmotic material.10. The process according to claim 1 wherein the oil continuous phasecomprises in addition sucrose octyl stearate, a polysaccharide,polyethylene glycol, esters of polyethylene glycol, esterified polyol,saccharide ester, or wax.
 11. The process according to claim 1 wherein awater soluble polymer is added in addition to the multifunctionalacrylate.
 12. The process of forming a population of microcapsulesaccording to claim 1 wherein the oil continuous phase is selected fromthe group consisting of isoamyl benzoate, capric triglyceride, caprylictriglyceride and blends thereof.
 13. The process of forming a populationof microcapsuies according to claim 1 wherein forming or crosslinkingthe prepolymers is accomplished by heating the mixture or exposing themixture to actinic radiation or both.